If you are an occasional freelancer (for programmer, sysadmin, etc.), do you need business insurance, even if you aren't really an official "business"? Assume for this you are doing things on UpWork or a site like that.
You'll need an insurance but only if you're dealing with large businesses, and the amount of the contract is significant. That's generally reserved for an agency. If you're just working as a causal programmer, mostly likely not.
Upworks jobs are small; serious and large jobs won't goto the open market. Those large jobs might require an insurance, but you aren't going to see them.
If someone askes you to buy an insurance on Upworks, think about the risks. Insurance is quite complicated for an oversea client. Unless the amount is very significant (unlikely), don't bother.
This is really a relative question considering the concept of insurance, what country you're doing business in, what your local licensing and business laws require, etc., but to try to give you a rough idea, the TL;DR is basically NO, you do not require it, nor, in my opinion, do you even really need it. However, UpWork has an alternative argument posted on their website here.
Insurance is always nice to have if or when you need it, but Business Liability Insurance rates are ridiculously low because most small businesses don't end up needing what it covers. Ten years ago I owned a few mall kiosks, most lease agreements required insurance with $1,000,000 Aggregate Limit, I was paying like $10 or $20 a month for it. Here's an article that touches on a couple scenarios and where the cost of insurance and benefits come into play.